Manufacture of artificial cellulose products



Patented Nov. 22, 1938 1 UNITED STATES MANUFACTURE OF ARTIFICIAL OELLULOSE PRODUCTS Walther Schieber, Berlin, and Walter Harz, Dormagen-I. G. Werk, Germany, assignors to I. G. Farbenindustrie Aktiengesellschaft, Frankfort on-the-Main, Germany No Drawing. Application October 8, 1935, Serial No. 44,124. In Germany October 9, 1934 3 Claims.

The present invention relates to the manufacture of artificial cellulose products, such as artificial silk, staple fiber, ribbons, films and so on, by a wet precipitation process.

It is known to precipitate cellulose from its solutions, for example cuprammonium or viscose solutions, initially in the form of a still very plastic mass with the aid of weak coagulating agents, and then, for final completion, to treat the still plastic mass in other baths. For example, in the stretch-spinning process for the manufacture of cuprammonium artificial silk, a still plastic thread is initially produced by extruding the cellulose solution into water, the thread being then hardened by an after-treatment with sulphuric acid. It is also known that the initial coagulation process can be influenced, for instance, by varying the temperature or by adding to the precipitation water small quantities of other substances, such for instance, as

' carbonates, carbonic acid or the like.

In accordance with the present invention, in a precipitation process of the kind described above, the addition to the precipitation water of small quantities of a phosphoric acid or a phosphate is particularly advantageous for the quality of the resulting cellulose product. For example, if o-phosphoric acid is added to the precipitation bath in the stretch-spinning process for the production of cuprammonium artificial silk, the silk obtained is much softer than that obtained by spinning with water only. The capillary fibers are well isolated, they do not stick together, and the resulting thread is non-fuzzy, without any reduction of the breaking strain and the extensibility. On the other hand, the said addition renders it possible to reduce the temperature of the precipitation bath, or, if the usual temperatures are maintained, to increase the velocity of the spinning process.

Ortho-, and metaand pyro-phosphoric acid and their water-soluble salts such, for instance, as monosodium-ortho-phosphate or dipotassium ortho-phosphate have proved to be advantageous. If ortho-phosphoric acid is employed, the quantity added may not exceed 0.3 gm. per liter, since, at higher concentrations, the coagulating power on cellulose solutions is again diminished; this is, however, not the case with the phosphoric salts. The phosphoric acid or the water-soluble salt thereof are added to the precipitation bath in an effective amount which in the case of phosphoric acid must not exceed about 0.3 gm. per liter and in the case of water-soluble salts of phosphoric acid must not exceed about 0.5 gm.

per liter. The term effective amount used hereinafter is intended to cover concentrations of phosphoric acids which do not exceed about 0.3 gm. per liter and concentrations of watersoluble salts of phosphoric acids which do not exceed about 0.5 gm. per liter.

The effect of the phosphoric acids and their salts is not impaired by the presence of such other substances as are usually added to the precipitation bath. For example, the effect of the phosphoric acid remains unimpaired even if the precipitation bath contains usual concentrations of sodium chloride, sodium sulphate, sodium bicarbonate, carbonic acid or the like.

The following examples illustrate the invention, the parts being by weight:

Example 1 A thread is spun with a velocity of 40m/sec. from a cuprammonium cellulose solution containing 7% of cellulose, 3% of copper and 7% of ammonia into a solution of ortho-phosphoric acid in distilled water at 32 C. containing 0.25 gm. per liter.

The silk obtained is soft, the capillary fibers do not stick together, the breaking strain amounts to 180 gm. per 100 ds. and the extensibility to 14.2%.

Example 2 Instead of the phosphoric acid in Example 1, 0.40 gm. per liter of disodium ortho-phosphate are employed. The silk obtained corresponds to that obtained in Example 1. The breaking strain in the dry condition amounts to 185 gm. per 100 ds. and the extensibility in the dry condition amounts to 13.5%.

Example 3 If, in the stretch-spinning process for cuprammonium artificial silk, a precipitation bath is employed which contains 0.5 gm. per liter of trisodium ortho-phosphate and moreover per liter 0.15 gm. of sodiumbicarbonate, 0.3 gm. of carbon dioxide and 0.18 gm. of sodium sulphate, and if the conditions of working are the same as in Example 1, a silk is obtained which shows a breaking strain in the dry condition of 175 gm. per 100 ds. and an extensibility in the dry condition of 15.2%.

Example 4 A xanthate solution of the usual composition,

cial products from cuprammonium'cellulose solu-' tions according to the stretch-spinning method the step which comprisesxprojecting a cuprammonium cellulose solution into a weakly coagulating aqueous liquid, which effects an initial coagulation but not a final hardening of the product, containing dissolved therein a phosphoric acid compound selected from the group consisting of phosphoric acids in amounts not exceeding 0.3 gm. per liter and water soluble salts thereof in amounts not exceeding 0.5 gm. per liter.

2. In the process for the manufacture of artificial filaments from cuprammonium cellulose solutions according to the stretch-spinning method the step which comprises projecting a cuprammonium cellulose solution into a weakly coagulating aqueous liquid which effects an initial coagulation but not a final hardening of the filaments containing dissolved therein at the most r 0.3 gm./l of ortho-phosphoric acid.

3. In the process for the manufacture of artifiicial filaments from cuprammonium cellulose solutions according to the stretch-spinning method the step which comprises projecting a cuprammonium cellulose solution into a weakly coagulating aqueous liquid which effects an initial coagulation but not a final hardening of the filaments containing dissolved therein at the most about 0.5 gm. per liter of a water-soluble salt of a phosphoric acid.

- WALTYHER SCI-HEBER.

WALTER. HARZ. I 

